The present invention relates to an optical reader system such as a facsimile transmitter and, more particularly, to a read-out level compensation system in an optical reader system.
It is very difficult in an optical reader system to obtain a uniform output because a video signal derived from sensor outputs inevitably includes variations due to the following reasons.
(1) The light source, usually a fluorescent lamp, includes variations in its brightness distribution. PA1 (2) A lens is necessarily required in the optical reader system and, therefore, the shading effect is unavoidably generated at the periphery of the lens. PA1 (3) The sensitivity of the sensor elements can not be uniform.
The above problems (1) and (2) can be minimized mechanically. However, it requires a long time period to adjust the system in a preferred condition. If the above problem (3) is desired to be removed, manufacturing cost of the sensor elements becomes considerably high.
Accordingly, an object of the present invention is to provide an optical reader system which ensures an accurate operation.
Another object of the present invention is to provide a read-out level compensation system in a facsimile transmitter system.
Still another object of the present invention is to provide a read-out level compensation system which uniforms an output signal derived from sensor elements in an optical reader system.
Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
To achieve the above objects, pursuant to an embodiment of the present invention, an optical reader system is constructed to first read out the white background to obtain a reference output. The reference output is reversed and memorized in a memory. The actual sensor output derived from an original sheet is multiplied by the memorized, reversed reference output to get a compensated video signal.